@Nitrogen Yup, the pin goes up and down like normal, the fault is 100% with the deadlock mechanism inside the main lock unit.
So, I'm VERY pleased to say, wondrous things happened today!
I moved the drivers seat forward as far as it would go to allow me access to the door panel trim T20 screw in the lower corner of the door panel. Once I slid the seat forward I then went to disconnect the battery, then came back and removed the screw.
Then I realised I'd have to reconnect the battery again in order to slide the seat backwards to allow me some room to start removing the rest of the door panel (the main door panel, not the hidden-away carrier plate).
So I reconnected the battery and I thought on the off-chance of it working, I pressed the button for the central locking to unlock all the doors. I heard all the usual noises and the door was still refusing to unlock. Then for some reason I thought what if I try to unlock the doors now using the remote key fob.
OMFG IT WORKED!!
I have NO idea how, but the action of me disconnecting the battery, waiting x amount of time, reconnecting the battery and then unlocking the doors with the remote keyfob (NOT the unlock button in the door panel itself) before I even tried it I knew it had worked because I heard the extra "whir" noise of the deadlock motor moving - something I've not heard it do since the day it broke.
Now quite sure why it worked this time I don't know? Every day since it broke (weeks ago) I have unlocked the doors with the key fob in the usual manner and the door refused to open. Disconnecting the battery has somehow reset *something* which meant that this time when I pressed the unlock button on the fob, it actually released the deadlock too.
Amazing...
FYI, I tried setting off the alarm too, that didn't do anything either.
So now I'm in a VERY relieved state of mind!
On monday I'll order a new lock mech (thanks for the part number
@Stig0r !) and we'll be sorted.
The one thing I need to be careful of now is to NOT let the deadbolts activate. So in other words, I must NOT let the alarm 'set'.
I tried a few things, in order to lock the doors, but not let the deadbolts kick in too.
It seems that if you press the central locking button on the drivers door, then shut the door, it actually arms the alarm - I instantly hit the UNLOCK button on the key fob before the deadlocks came in (approx 30secs after the alarm sets).
The only way I can get all the doors to lock (and the boot/trunk) is to start the engine with all the doors shut, press the central locking button (so all doors & boot lock), turn off the engine, get out, and before closing the drivers door I can press the lock pin down on the drivers door, then shut the door.
This leaves all doors and boot/trunk locked, but ensures the deadlocks do not kick in.
I just need to remember to NOT lock the car with the key fob until I get my new lock mech
Thank you
everyone for this amazing thread, the superb photos and detailed explanations and as ever, the incredible member support.
Once I get the old lock mech replaced (it'll be approx 2wks time), I'll do the same thing as Stig0r and bust it open to see if mine has suffered the same fate.